Pneumatic warning horns are common devices found on locomotives or other freight hauling railroad equipment. Supplied by companies such as Wabtec, Inc., locomotives have employed pneumatic warning horns or devices for many years. The majority of these locomotive horns have their air feed controlled by a manual operation performed by a locomotive engineer. However, Wabtec, Inc. has manufactured an automatic pneumatic warning or signaling device for use on a freight locomotive. This automatic device is called a type “C” engine signal valve, and is designed to have the locomotive warning horn emit sound for a similar length of time regardless of the number of cars in a train. The type “C” engine signal valve utilizes two diaphragm assemblies and a stem type valve to control the intermittent rate of operation. This valve is quite complex, making it expensive to manufacture and maintain.
While warning horns are, and signal valves may be, commonplace equipment on locomotives, they are not commonplace on freight cars. Since freight cars have not typically traveled without being connected to a locomotive, freight cars have not previously needed to employ warning devices. However, with the advent of special freight cars carrying pneumatically operated ramps that may be raised and lowered while not connected to a locomotive, warning devices are now needed on such freight cars as well. In this context, the warning device is to inform people to stay clear of the pneumatically operated ramp as it is raised and lowered at the end of the freight car.